TO CHEMICAL FERTILIZERS 



Kxcessive applications to the cereal crops of nitrogenous 

 manures frequently cause those crops to " lodge," or fall 

 down in wet weather, owing to the effect on the leaf and stem 

 of excessive growth, stimulated by too much nitrogen ; at 

 the same time, the quality of the grain is often inferior, and 

 the date of ripening unduly delayed. The general tendency 

 of heavy dressings of nitrogenous manures is to increase the 

 period during which ripening takes place, and, in the case of 

 root crops, to lower their keeping qualities, to render them 

 more watery, and to increase their susceptibility to fungoid 

 and bacterial decay. Nevertheless, sufficient quantities 

 of available nitrogen are absolutely essential for large crop 

 yields. On the lighter soils in the wetter climates, sulphate 

 of ammonia is generally preferable to nitrate of soda, but 

 much will depend upon the amount of available lime and upon 

 the other fertilizers which the farmer proposes to use. The 

 general result of the addition of nitrogen as applied to the 

 crops at Rothamsted can be best described by quoting from 

 Russell's " Soil Conditions." He says : " The first addition 

 of nitrate causes a marked rise in the weight per grain and 

 the proportion of grain to total produce, but successive 

 additions show no further rise. Indeed other experiments 

 prove that excess of nitrogenous food causes the proportion 

 of grain to fall off somewhat. The leaf and the general 

 character of growth are affected to a much greater extent. 

 Nitrogen starvation causes yellowing of the leaf, especially 

 in cold spring weather, absence of growth, and a poor starved 

 appearance generally : abundance of nitrogen, on the 

 other hand, leads to a bright green colour, to a copious growth 

 of soft, sappy tissue, liable to insect and fungoid pests (appar- 

 ently because of the thinning of the walls and some change 

 in composition of the sap) and to retarded ripening : the 

 effects resemble those produced by abundant water supply. 

 A series of plants receiving varying amounts of nitrate are 

 thus at somewhat different stages of their development at 

 any given time, even though they were all sown on the same 

 day, those supplied with large quantities of nitrate being less 

 advanced than the rest. If they could all be kept under 



